Hip, Knee Replacement Raises Heart Attack Risk

< Jul. 25, 2012 > -- Getting a new hip or knee is an increasingly common procedure in the U.S., but a new study warns that people who have these surgeries have a 30 times greater chance of a heart attack within two weeks afterward.

The risk drops fairly quickly after that for knee replacements, but stays high for about six weeks for hip replacements, researchers say.

Each year in the U.S., surgeons do 676,000 knee replacements and 327,000 hip replacements, the CDC says.

Researchers at Utrecht University in the Netherlands looked at data on more than 95,000 people who had knee or hip replacement surgery in Denmark between January 1998 and December 2007.

They compared heart attack risk in the participants with more than 286,000 others who didn't have joint replacement surgery.

Risk boosted

They found that the risk for heart attack in hip replacement patients increased by 25 times in the first two weeks after surgery and by 31 times for knee replacement patients. The risk lingered for a total of six weeks in those who'd had hip replacement surgery.

At six weeks after surgery, the absolute risk of a heart attack then dropped to 0.51 percent in people who had hip replacement and 0.21 percent in those who had knee replacement.

People at highest risk for heart attack were at least 80 years old, the researchers found. Those at high risk also had other risk factors for heart attack: They had a previous heart attack, heart failure, or blood vessel disease; they took nonsteroidal anti-inflammatory drugs, beta blockers, certain diuretics or blood-thinners; or they were men.

Effects of surgery

What caused the increased risk? Lead researcher Arief Lalmohamed, Pharm.D., blames the side effects of the surgery. The aftereffects of anesthesia on the heart and blood vessels, as well as blood loss, irregular heartbeats, and lack of oxygen during surgery could all have an impact.

"In addition, the period before surgery itself is a very stressful time for the patient; even thinking about surgery increases cardiac risk," says Dr. Lalmohamed.

Another possibility, especially in hip replacement surgery, is that bits of bone marrow may be released into the bloodstream. The marrow emboli could travel to the heart and cause a heart attack.

More data needed

The researchers say one drawback to their study is that the data they used did not have information on other risk factors for heart attack - for instance, whether participants smoked or had high blood pressure, and whether their body mass index was high.

Gregg Fonarow, M.D., at the University of California, Los Angeles, says that the risk for heart attack after joint replacement surgery can be lessened by thoroughly assessing each person before surgery, prescribing certain medications, and carefully monitoring the person in the first two to six weeks after the procedure.

The study was published online this week in the Annals of Internal Medicine.

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Hip Replacement Surgery

Hip replacement operations usually take about two hours, and you'll typically stay in the hospital afterward for three to four days.

The new hip parts may be cemented in place or they may be made of porous material that allows your own bone to grow into the replacement parts to hold them. Sometimes, the surgery includes both cemented parts and uncemented parts.

After discharge from the hospital, you may need to stay at a rehab center for a few days, especially if you live alone.

Recovery from a hip replacement varies, depending on the type of surgery and how well your rehab goes. Most people use a walker for about four weeks after the surgery and start driving within two to four weeks. Most people gradually increase their activities and can play golf, doubles tennis, or bowl after about 12 weeks. Doctors usually don't recommend more active sports, such as singles tennis and jogging.

Always talk with your health care provider to find out more information.

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